[Java][Flight][Tests] Add roundtrip tests for Java Flight Test Client

There should be some built-in roundtrip tests for Java Flight IntegrationTestClient

**Reporter**: [Bryan Cutler](https://issues.apache.org/jira/browse/ARROW-7933) / @BryanCutler
#### Related issues:
- [[Integration][Java] null type integration test](https://github.com/apache/arrow/issues/24122) (is related to)

_{**Note**: *This issue was originally created as [ARROW-7933](https://issues.apache.org/jira/browse/ARROW-7933). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}

Start by locating the Java Flight IntegrationTestClient and reviewing the related null type integration test issue. Determine which roundtrip cases the built-in tests should cover and how existing integration tests are run. Done means the Java Flight Test Client has the requested roundtrip coverage.

Written by the indexing model from the issue text.